In today's wireless communication systems, the demand for mobile location services is growing, both from consumers and from authorities. Location is a vital component in consumer services such as social media, search, advertising, and navigation. In the US, and many other countries, emergency positioning performance is a regulatory requirement. In the US, such E911 requirements are very important—loss of performance is not an option. In addition, mobile location can be used by authorities for road-traffic management and for machine-to-machine purposes.
Recently, some implementations of bandwidth reduction radio functionality have been presented. For example, one such functionality is reducing the WCDMA downlink (DL) bandwidth to 4.2 MHz, from 5 MHZ. The reason is that operators want to use a part of the WCDMA spectrum for GSM traffic, or other traffic if possible.
One consequence of the reduction in bandwidth on the downlink is that the DL filtering performed by the so-called RRC (Root-Raised Cosine) filter in the base band (BB) is altered, to narrow down the DL spectrum. Doing so, emission requirements still need to be maintained. Laws of nature then inevitably means an increase of side lobe levels in the time domain. This, in turn affect user equipment (UE) receivers in that their detection signal processing become more prone to false detections, detecting energy in a side lobe, instead of the desired main lobe.
Within current technology, this has affected one crucial positioning measurement, namely the so-called UE RxTx type 1 measurement. Lab trials show that this measurement becomes biased due to occurrence of side lobes; therefore, the calculated distance between the radio base station (RBS) and the UE can become negative when the UE is close to the base station. This results in a failure of Round Trip Time (RTT) positioning, which in turn deteriorates the overall positioning performance.
Consequently, there is a need for enabling improved positioning during bandwidth reduction induced errors in the position measurements.